Trellis phase modulation coding - Minimum distance and spectral results

We present a new method of continuous phase-shift modulation, and investigate its error and spectral properties. The new method can be viewed as a generalization of minimum shift keying. A constant amplitude signal carries a coded sequence of linear phase changes; the possible signal phases form a trellis in phase and time. Simple codes, using 4-16 phases, together with a Viterbi algorithm decoder, allow transmitter power savings of 2-4 dB over binary PSK, in a much narrower bandwidth. A method is given to predict error performance, and the error rates of all useful codes are given. A software-implemented decoder is tested on a simulated Gaussian channel. Finally, a general expression for the power spectral density is presented, with a sample spectrum shown to illustrate the band-limited nature of the method.